The optical windows and domes employed in missile systems for infra-red imaging demand good mechanical stability and high optical transmission in the wavelength range between 0.4 micron and 12 microns. Zinc sulfide, zinc selenide, germanium, gallium arsenide, gallium phosphide, mercury cadmium telluride and cadmium telluride are used in applications such as missile domes which requiring long wavelength infrared transmission capability. Germanium is extremely expensive due to its low availability in nature. The fabrication of zinc sulfide and zinc selenide via CVD routes is problematic due to use of toxic gases, and is not an environmentally benign process. Moreover, the cost of production is very high due to low yield.
Zinc sulfide is a window material for long wave-infrared (LWIR) and semi-active laser dome is multispectral Zinc Sulfide (ZnS), made by chemical vapor deposition. An alternative route to make more erosion-resistant and ultra-high density ZnS could be via hot-press and vacuum sintering route followed by anti-reflective coatings to produce IR windows that are highly erosion-resistant to sand and rain at high altitude flight environments.
A low cost IR window is a mandatory requirement in order to be able to market an affordable vision enhancement system for aircraft, automotive and other high volume applications. The cost of the IR window is a major factor in the viability of offering an IR device for general use. The potential safety benefits to the driving public are enormous. Many lives could be saved and needless destruction of automobiles could be prevented if such a device were available at a reasonable cost. Hence, there is tremendous need exists for the production of a low cost IR window [1].